Cultists are trying to create a Madness Network, a set of Ritual Sites connected to an evil dimension through Portals. Plan carefully to create the biggest Madness Network while separating it from the ordinary people of your cities. Each Round, you will have the option to open new Portals at the edges of your board and add a Ritual to your Madness Network. At the end of the game, you will gain points for your connected Rituals and Portals, but any Exit that is connected to either of those will not count when scoring regular Networks.
Reality is tearing itself apart with the Portal Expansion, and immense holes are opening, showing glimpses of the unthinkable. But not all that is supernatural will hurt or scare. You can safely travel to work by going through these portals of doom. Open Portals to connect distant areas of your Network as if they were next to each other. However, not all Portals are the same: there are three kinds of Portals (marked with the letters A, B, and C) and only two Portals of the same kind (same letter) are connected to each other. There can never be more than 2 Portals of the same kind on your board.
Tentacles are entering your little safe oasis of sanity, but a little madness is ok. Try to have as many Tentacles as possible in your territory and make people lose their minds while driving next to them. Each round, the Tentacle die will tell you the length of the Tentacle to draw that Round; at the end of the round, you may add it to your board. If you do, you will choose its starting position and its shape. Tentacles can share spaces with Railways and Highways. At the end of the game, you will gain points for each Tentacle you drew, plus bonus points for each space occupied by both a Tentacle and a Highway or Railway.
Mysterious things are happening in your county! Send your Investigator to collect Clues that are appearing on your board and solve the case. Every turn you can spend a number of Movement points equal to the footsteps shown on the Investigation die to move your Investigator to an adjacent space connected to their starting space with a Highway Route, or move your Investigator from a space with a Station (or from a Railway Exit) to a space with a Station connected to their starting space from at least a Railway Route. If you mange to collect all Clues, you will solve the mystery (and get bonus points)!